1. Field of the Invention
The present invention relates to a friction button for fastening to a clutch disc. More specifically, the present invention relates to a friction button for fastening to a clutch disc where grooves and/or contours are formed in a face of the clutch button for improved clutch release.
2. Description of the Prior Art
Typically, a plurality of clutch buttons are fastened to a motor vehicle clutch disc. The clutch disc assembly is used in a clutch assembly to transmit drive forces from a prime mover such as an internal combustion engine to an input shaft of a transmission, which in turn multiplies the torque by a selected gear ratio and transmits it to an output shaft such as a vehicle driveshaft. Prior art clutch buttons often have a backing plate on which a friction material is fixedly disposed. The buttons are spaced circumferentially about the clutch disc with the friction material facing outwardly. The buttons are commonly fixed to the disc by riveting the backing plates to the disc. The disc is selectively engaged with a drive disc, commonly a flywheel, to transmit a rotational driving force to an output shaft. A spring loaded engagement member, such as a pressure plate, presses the clutch disc against the drive disc in the engaged condition. The frictional engagement causes the clutch disc to rotate with the flywheel. Commonly, the friction material has both a smooth continuous inner face which is bonded to the backing plate and a smooth continuous outer face which contacts the drive disc (flywheel or pressure plate).
One problem with the prior art clutch assemblies is that the clutch disc tends to remain in contact with either the flywheel or the pressure plate even if the clutch is disengaged, especially when the clutch is at an elevated temperature. The resultant undesired frictional drag on the clutch disc causes difficulty in the selecting the desired transmission gear ratio.
Configuring the friction material to facilitate cooling is believed to facilitate certain aspects of clutch performance. Indeed, it is known to provide a spacing between portions of the clutch button friction material to facilitate cooling of the friction material. U.S. Pat. No. 5,158,165, assigned to the assignee of this application, discloses spacing portions of friction material from each other to form a central void to facilitate air movement therebetween for improved cooling of the clutch button. It is also known to provide a plurality of radially extending grooves in the face of a friction material to facilitate fluid movement across the face for improved cooling of the friction material and of the structure to which it is mounted. However, while the known spacings and grooves facilitate cooling, they are not well suited to facilitating the separation of the disc from the pressure plate and flywheel.
It would be desirable to provide a clutch which features a low drag torque on the clutch disc when the clutch is disengaged. Enhancing separation of the clutch disc from the drive disc (flywheel) when the clutch is disengaged would yield this result.
According to the present invention there is provided a disc type clutch for rotationally coupling a drive disc which flywheel or pressure plate to a shaft (transmission input shaft) having an enhanced separation action of the clutch disc from the flywheel when the clutch is disengaged. Friction material in the form of a plurality of friction pads are bonded to a backing plate to form a clutch button or bonded directly to the clutch disc to form a clutch disc assembly. The clutch buttons of the present invention have circumferential grooves formed in the face of the button which aid in the separation of the clutch disc assembly from the flywheel due to the aerodynamic forces generated by airflow through the separate grooves. A secondary effect is that operating temperature of the clutch disc assembly and especially the clutch buttons are reduced due to the additional cooling airflow created by the grooves formed in the face of the friction material that contacts the flywheel and/or pressure plate when the clutch is engaged.
The circumferential orientation of the grooves increases the aerodynamic forces that enhance the separation characteristics of the clutch disc from the flywheel and/or pressure plate. Also, the volume of air flowing through the grooves is increased as compared to prior art designs using radial grooves.
One provision of the present invention is to enhance the separation characteristics of a clutch disc from a drive disc.
Another provision of the present invention is to enhance the separation characteristics of a clutch disc from a drive disc by using aerodynamic forces.
Another provision of the present invention is to enhance the separation characteristics of a clutch disc from a drive disc by using aerodynamic forces generated by at circumferential grooves formed in a friction button attached to the clutch disc.
Another provision of the present invention is to increase the cooling of a clutch disc by increasing the airflow across the surface of the clutch button attached to the clutch disc.
Still another provision of the present invention is to increase the cooling of a clutch disc by increasing the airflow across the surface of a clutch button attached to the clutch disc with at least two circumferential grooves formed in a face of said clutch button.